It could be an Eley .477 Breech Capping Cartridge but, I’m not sure.
I have included a coin in the photograph, to try to give some appreciation of size. Have also tried to peer into the ends, but, without much success.
Understand that it could also be some kind of recent production.
I’m reluctant to pull it apart…therefore; would greatly appreciate help in identification, or any additional background information.